Ultraviolet light permeable filter for flaw detection light, and method for detection of flaws

ABSTRACT

An ultraviolet light permeable filter for an ultraviolet detection light is equipped on a filter glass surface with a dielectric multi-film layer which allows a visible radiation of wave length from 694 nm to 780 nm to reflect on the layer. The wave length also does not penetrate through the multi-flim layer. This filter prevents a reddish halation occurrence during an inspection display of a flaw detection light, which is the main cause of overlooking a scratch or flaw pattern.

This present disclosure relates to subject matter contained in JapanesePatent Application No.11-338041 (filed on Nov. 29, 1999) which isexpressly incorporated herein by reference in its entirety

BACKGROUND OF THE INVENTION

The present invention relates to an ultraviolet light permeable filterfor a flaw detection light and a method for a detection of flaws.

In a prior art, according to JIS (Japan Industrial Standard), in orderto perform a fluorescent penetrant liquid detection method test and afluorescent magnetic powder detection (=magnaflux) method test, anultraviolet detection light (this is also called a black light amongthose skilled in the art) is adopted, wherein the light is emitted froma metal halide lamp and an ultraviolet light filter so that thefluorescent penetrant liquid and magnetic powder are excited to emitradiation.

For example, in the method as already disclosed, the ultraviolet flawdetection light comprising the metal halide lamp and the ultravioletlight permeable filter equipped with a minimum wave length of 385±5 nmwhich can be recognized with normal eyesight is provided. An inspectorcan lessen his fatigue or avoid his mistakes caused by fatigue duringblue-violet radiation using a wave length below 400 nm.

In the field test of the fluorescent penetrant liquid method or thefluorescent magnetic powder method for checking a flaw on an irregularsurface in a minor area where a marketed ultraviolet flaw detectionlight comprising the ultraviolet light permeable filter and the metalhalide lamp is used, a serious problem exists. The inspector hasdifficulty in checking the flaw because he is forced to recognize withhis eyes a reddish halation mixed by a red and pale blue radiationswhich are caused by reflected light from a test display according to theangle between radiated light and the inspector's eyes toward thedisplay. When the flaw exists on the spot of the halation, especially areddish halation, the inspector might miss checking the relative flaw.As a result, an accurate flaw detection cannot be attained by theinspection on an irregular surface in a minor area for finished work.

SUMMARY OF THE INVENTION

The present inventor has done research and experiments to provide anultraviolet light permeable filter which prevents the occurrence ofhalation, especially reddish halation which is the main cause ofoverlooking a flaw during the inspection. As a result, this inventor hasconfirmed that visible radiation wave length in the ranges of 380 nm˜410nm and 694 nm˜780 nm penetrates through a prior marketed ultravioletlight permeable filter. This prior art uses various kinds of ultravioletflaw detection lights composed of metal halide lamps. The radiation inthe above ranges reflects on the test display to produce a reddishhalation. At the same time, the inventor has found that the reddishhalation is avoided when the radiation in the range of 694 nm˜780 nmdoes not penetrate the filter.

In order to realize the above purpose, the following procedures areadopted.

This invention provides a device of a dielectric multi-film layer whichis formed on the surface of the ultraviolet light permeable filterglass, whereas visible radiation in the range of 694 nm˜780 nm reflectson the filter and does not penetrate therethrough.

The invention also provides a device of the filter where the dielectricmulti-film layer is composed of plural layers of low refractivitymaterial and of high refractivity material stacked in alternating layersof low refractivity and high refractivity material.

This invention further provides a device of any filter as mentioned sofar where the multi-film layer is while a layer of high refractivitymaterial is sandwiched between layers of low refractivity material andthe obtained composite is a plurality of layers thick.

Further, the flaw detection light of the present invention is equippedwith any of said filters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial diagrammatic view of longitudinal section showing aconstitution of an ultraviolet light permeable filter to be equippedwith a flaw detection light in an embodiment No.1.

FIG. 2 is a partial longitudinal section view showing enlargedconstitution of a plurality layers of the filter as illustrated in FIG.1.

FIG. 3 is a partial longitudinal section view showing enlargedconstitution for a single layer (13) which is composed of membranes (14and 15).

FIG. 4 is a partial longitudinal section view showing a constitution ofan ultraviolet light permeable filter for a flaw detection light inaccordance with an embodiment No.2.

FIG. 5 is a partial longitudinal section view showing an enlargedconstitutional condition for a dielectric multi-film layer placed onboth surfaces of the filter as illustrated in FIG. 4.

FIG. 6 is a partially schematic side view of a flaw detection light.

FIG. 7 is a graphical representation of a spectrophotometric curve lineobtained by a metal halide lamp in this invention.

FIG. 8 is a graphical representation of a spectrophotometric curve lineobtained by a prior ultraviolet light permeable filter glass.

FIG. 9 is a graphical representation of an ultraviolet light permeablefilter obtained by this invention.

FIG. 10 is a graphical representation of the other ultraviolet lightpermeable filter obtained by this invention.

FIG. 11 is a graphical representation of another ultraviolet lightpermeable filter obtained by this invention.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENT

First, the inventor's research and experiments are explained.

With reference to FIG. 6, the numeral 1 is a metal shell having anopening (2) on its side for radiating an ultraviolet light. The numeral3 is a basic substratum of a filter of the ultraviolet light equippedwith the opening (2). At the rear of the filter (3), a concave reflectormirror (5) is arranged with an anodized mirror face (4) which isdirected for the filter (3). On the middle portion of the mirror (5), ahole (6) is drilled. The numeral 7 is a metal halide lamp which isinserted into the hole (6) through the back side of the mirror (5),while its basic portion is connected into a socket (8). A power supplybinary cord (9) is connected with an inverter (not shown) at the outsideof the shell (1). The numeral 10 is a handle portion in which the cordis running through.

According to FIG. 7, a graphical representation of a spectrophotometriccurve for the metal halide lamp (7) is shown. This lamp is adopted fromone marketed in the name of “70W/FDA” supplied by Marktec Corporation.FIG. 8 is a graphical representation of a spectrophotometric curveobtained by a prior ultraviolet light permeable filter glass. Thisfilter is known by the name of “D10FA” marketed by Marktec Corporationwherein no coating is furnished thereupon. As shown in FIG. 8, thefilter glass in the prior art, against visible radiation in the wavelength range of 380 nm˜780 nm, allows the visible radiation in the wavelength of 413 nm ˜694 nm to be absorbed and the radiation does notpenetrate therethrough, while the filter allows the radiation in thewave lengths of 380 nm 413 nm and 694 nm˜780 nm to penetratetherethrough.

In order to produce the graphical representation of the curve in thisinvention, a special spectrophotometer for such presentation developedand supplied by Shimadzu Seisakusho Co., Ltd., model No. U-2200 wasused.

TEST

Experimental Material: Steel square column, in the sectional size of50×50 mm, with 200 mm long.

Scratch: Natural scratch in 20 mm long and 0.12 mm deep on the polishedsurface.

Fluorescent magnetic powder: Name of “Supermagna LY-50” supplied byMarktec Corporation.

Density of magnetic powder: 0.5 g/1

Dispersing agent: Name of “BC-1” supplied by Marktec Corporation.

Density of dispersing agent: 2 g/1

Electric current value of magnetization: DC-500A

Under above conditions, several visual observation tests were performedto watch occurrence of halation on the indicated scratch.

As a first test, a prior art ultraviolet light permeable filter glasswas equipped with a flaw detection light and a fluorescent magneticpowder test was performed. As a result, a pale blue halation could notbe recognized, but a reddish halation was recognized, which causedoverlooking of the indicated scratch thereon.

In order to improve the result, in stead of the prior art filter, twokinds of the newly invented filters which were equipped with adielectric multi-film layer obtained by vacuum evaporation method,having graphical representations as shown in the curves of FIG. 9 andFIG. 10, are then tested.

As a second test, the filter which allows the visible radiation over thewave length of 700 nm to reflect and which has the graphicalrepresentation of the curve in FIG. 9 was equipped with the flawdetection light and the fluorescent magnetic powder test was performed.As a result, the pale blue halation was recognized while the reddishhalation was not recognized, whereas the indicated scratch was clearlyobserved.

As a third test, the filter which allows the visible radiation in thewave lengths of 400 nm 410 nm and over nearly 700 nm to reflect andwhich has the graphical representation of the curve in FIG. 10 wasequipped with the flaw detection light and the fluorescent magneticpowder test was performed. As a result, the pale blue halation was alittle bit recognized while the reddish halation was not recognized,whereas, same as the second test, the indicated scratch was clearlyobserved.

Through the above three experimentations and obtained results, thepresent inventor realized that where the radiation in the wave length ofnearly 700 nm was recognized as a reddish halation and that theoccurrence of this halation was the true source of an inspector'smistake. Therefore, the inventor has developed an ultraviolet lightpermeable filter which allows the radiation to reflect and not topenetrate in the range of wave length from nearly 700 nm to 780 nm, whenthis filter is equipped with a flaw detection light, the satisfactoryresult has been confirmed.

Now, actual embodiments for the present invention are explainedaccording to the attached drawings.

Embodiment 1

FIG. 1 is a partial diagrammatic view of longitudinal section for anultraviolet light permeable filter (11) equipped with a flaw detectionlight, and a constitution of the filter (11) is shown in clarifiedmanners, and the numeral 3 is also the substratum of the filter whilethe numeral 12 is a multi-film layer having plural layers. FIG. 2 showsa partial longitudinal section view for the multi-film layer (12)enlarged and having plural layers (13). FIG. 3 is also a partiallongitudinal section view for an individual layer (13) enlarged, whichis again composed of further three membranes (14 and 15). This filter(11) is obtained by forming a dielectric multi-film layer (12), whichcan reflect a visible radiation with a wave length range of 694 nm˜780nm, on the glass surface of a prior art filter. The layer of themulti-film (12) is composed of 8 layers (13). Each layer (13) is alsocomposed of other membrane layer (14) with low refractivity material andof another membrane layer (15) with high refractivity material, layers(14 and 15) alternately. In this situation, the high refractivitymembrane (15) is sandwiched by the low refractivity membranes (14).

The dielectric multi-film layer (12) may be formed by coating thinlayers (14,15) in alternate layers through vapour deposition, such as avacuum evaporation method or an ion plating method as are well known, sothat permeable wave length is selectively controlled. The vapourdeposition method is inexpensive.

The material for a single layer (13) of the multi-film (12) is selectedfrom a group of high refractivity materials such as HfO2 (Hafniumoxide), TiO2 (Titanium oxide), ZrO2 (Zirconium oxide), Zns (Zincsulphide) and from a group of low refractivity materials such as SiO2(Silicon oxide), MgF2 (Magnesium fluoride) and Na8AlF6 (Cryolite). Thisindividual layer (13) is composed of the low refractivity membranes (14)and the high refractivity membrane (15) in alternate layers. As shown inFIG. 3, the single layer of the multi-film layer is composed in thefollowing manner. First, on the low refractivity membrane (14) of SiO2material with 146 nm, the high refractivity membrane of TiO2 materialwith 520 nm is placed, and then on these combined membranes the lowrefractivity membrane (14) is again placed. Eight layers of thisobtained single layer (13) composed of three membranes (14, 15 and 14)are now stacked together, and thus the multi-film layer (12) iscompleted. Now, the layer (12) is attached on one side surface of theprior filter glass, whereas the visible radiation of wave lengths 694nm˜780 nm reflects on the filter (11) and does not penetratetherethrough.

The dielectric multi-film layer (12) is not necessary composed of 8layers, and when the number of the layer is increased the reflectiondegree of the radiation for wave lengths can be properly controlled. Theorder to alternate the membranes is explained as above, but this ordermay be changed as: First, the high refractivity membrane (15) is piledon the low refractivity membrane (14).

Embodiment 2

According to FIG. 4, the numeral 16 is an ultraviolet light permeablefilter, wherein a multi-film layer (17) is equipped on the other sidesurface of the previous filter (11) and the layer (17) allows visibleradiation at wave length of 400 nm˜410 nm to reflect on the layer (17)and this radiation does not penetrate the layer (17). With reference toFIG. 5, the numeral 18 is a single membrane layer which composes of themulti-film layer (17) with 8 layers stacked. This single layer (18) mayalso be composed of membrane layers (14) with low refractivity materialwhich alternate with membrane layers (15) with high refractivitymaterial as shown in FIG. 3.

As shown in FIG. 5, on the other side surface of the filter (11), themulti-film layer (17) of dielectric quality is attached to substratum(3). Eight single layers (18) are stacked, while the layer (18)comprises : a membrane layer (15) of high refractivity TiO₂ material at325 nm stacked on a membrane layer (14) of low refractivity SiO₂material at 91 nm and further the same low membrane layer (14) isstacked on the same high membrane layer (15), and thus the dielectricmulti-film layer (17) is obtained, whereas this dielectric layer (17)allows visible radiation in wave length at 400 nm ˜410 nm to reflect onthe layer (17) while the radiation does not penetrate therethrough. Forfurther references and clearer understanding, the examples of thepresent invention are now explained below to teach how to produce therequired filters:

EXAMPLE 1

On one surface of an ultraviolet light permeable filter glass (ArticleNumber D10FA supplied by Marktec Corporation without any coating on itsglass surface), a multi-film layer (12) is formed. The layer (12) isproduced by vacuum thin film evaporation treatment (Article Name andNumber:Automatic successive vacuum thin film forming machine, No. CES-3,supplied by Kabushiki Kaisha Synchron) and this filter before puttingthe layer (12) had a graphical representation of a spectrophotometriccurve shown in FIG. 8. On a low refractivity membrane (14) of SiO2material with 146 nm, a high refractivity membrane (15) of TiO2 materialwith 520 nm is placed, and further the same low refractivity membrane(14) is again placed thereon. In other words, the high refractivitymembrane (15) is now sandwiched by two low membranes (14) and this threelaminated composite becomes a single layer (13) for the multi-film layer(12). Thus, 8 layers of the obtained composite layer (13) are stackedtogether into the multi-film layer (12). In this method, the ultravioletlight permeable filter (11) is now completed as shown in FIG. 1˜FIG. 3.

With this filter (11), the graphical representation of thespectrophotometric curve is checked, and as a result, the relative graphis shown in FIG. 9, wherein the dielectric multi-film layer (12) whichallows a visible radiation of wave length 694 nm˜780 nm to reflect onthe filter (11) and not to penetrate therethrough is now confirmed.

The filter (11) is then equipped with a flaw detection light (ArticleName and Number: Super Light D-10, supplied by Marktec Corporation,operated by Metal Halide Lamp 70 W/FDA, also supplied by MarktecCorporation), and tested in the following data:

Experimental Material : Steel square column, in the sectional size of50×50 mm, with 200 mm long.

Scratch : Natural scratch in 20 mm long and 0.12 mm deep on the polishedsurface. Fluorescent magnetic powder : Name of “Supermagna LY-50”supplied by Marktec Corporation.

Density of magnetic powder: 0.5g/1

Dispersing agent: Name of “BC-1” supplied by Marktec Corporation.

Density of dispersing agent: 2g/1

Electric current value of magnetization : DC-500A

As a result of the test, pale blue halation is recognized while reddishhalation is not recognized, whereas the indicated scratch is clearlyobserved.

Example 2

Same as the Example 1, on one surface of the ultraviolet light permeablefilter glass, the dielectric multi-film layer (12) is formed, while onthe other surface of the glass filter, another dielectric multi-filmlayer (17) is formed. The latter layer is also produced by the vacuumthin film evaporation treatment as mentioned. On a low refractivitymembrane of SiO₂ material with 91 nm, a high refractivity membrane ofTiO₂ material with 325 nm is placed, and further said low refractivitymembrane is again placed thereon. This three laminated composite becomesa single layer (18) for the multi-film layer (17), and 8 layers of thesingle layer (18) are stacked together into the multi-film layer (17).Thus, the ultraviolet light permeable filter (16) is obtained as shownin FIG. 4 and FIG. 5.

With this filter (16), the graphical representation of thespectrophotometric curve was checked, and the result showed the graph inFIG. 11, wherein the dielectric multi-film layer (17) which allows avisible radiation of wave length with 405 nm˜410 nm to reflect on thefilter (16) and not to penetrate therethrough is now confirmed.

Same as Example 1, a test is performed thereof, through which nohalation is present with a good result observation of the indicatedscratch.

EXAMPLE 3

Same as the Example 1, on one surface of the filter glass, themulti-film layer (12) is formed. The multi-film layer is produced as: Ona low refractivity membrane of MgF₂ material with 138 nm, a highrefractivity membrane of HfO₂ material with 440 nm is placed, andfurther the low refractivity membrane is again placed thereon. Thisthree laminated composite becomes a single layer (13) for the multi-filmlayer (12) which is composed of 8 piled single layers (13). In thisprocedures, the filter (11) as shown in FIG. 1˜FIG. 3 is obtained.

With this filter (11), when the graphical representation of thespectrophotometric curve is checked, the similar graph shown in FIG. 9is obtained, whereas the dielectric multi-film layer (12) which allows avisible radiation of wave length with 694 nm˜780 nm to reflect on thefilter (11) and not to penetrate therethrough is confirmed.

With this obtained filter (11) a test is performed in the same mannersas Example 1, whereas blue halation is recognized but reddish halationis not recognized. Because of no existence of the reddish halation theindicated scratch can be clearly observed.

EXAMPLE 4

Same as Example 2, on one surface of the filter glass, the dielectricmulti-film layer (12) is formed. This layer (12) is composed of 8 stacksof a single layer (13). The single layer (13) is produced in thefollowing manners: on a low refractivity membrane (14) of MgF₂ materialwith 138 nm, a high refractivity membrane (15) of HfO₂ material with 440nm is placed, and further the low refractivity membrane (14) is againplaced thereon. On the other hand, on the other surface of the filterglass, another multi-film layer (17) is formed. The latter layer (17) isalso composed of 8 stacks of a single layer (18). The single layer (18)is produced in the manners: On a low refractivity membrane of MgF₂material with 138 nm, a high refractivity membrane of TiO₂ material with325 nm is placed, and further the same low refractivity membrane isagain placed thereon. In this procedure, an ultraviolet light permeablefilter (16) as shown in FIG. 4 and FIG. 5 is now obtained.

With this filter (16), when the graphical representation of thespectrophotomeric curve is checked, the similar graph shown in FIG. 11is provided, whereas the dielectric multi-film layer (17) which allows avisible radiation of wave length with 405 nm˜410 nm to reflect on thefilter (16) and not to penetrate therethrough is confirmed.

With this filter (16) a test is performed in the same manner as theExample 1, whereas no halation is recognized at all, and satisfactoryinspection result is attained with proper observation.

As explained so far, the present invention can provide an ultravioletlight permeable filter for a flaw detection light, the filter allowing avisible radiation in the wave length range from 694 nm to 780 nm toreflect on the filter and also allowing the radiation not to penetratethrough the filter.

At the same time, when the invented filter as explained in thisspecification is equipped with an ultraviolet flaw detection light, theflaws and scratches can be promptly and easily found by inspectors, evenon plane surfaces and well polished or well finished faces which arevery difficult in the prior art.

It is now clearly understood the described invention shall greatlybenefit present and relative industrial field for finding flaws orscratches with ease.

It is further understood by those skilled in the art that the foregoingdescriptions is a preferred embodiment of the disclosed device and thatvarious changes and modifications may be made in the invention withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. An ultraviolet flaw detection light wherein thelight is equipped with an ultraviolet light permeable filter comprisinga dielectric multi-film layer which allows a visible radiation of a wavelength range from 694 nm to 780 nm to reflect on the filter whichprevents penetration of the wave length range from 694 nm to 780 nmthrough the filter and wherein the filter is on a surface of anultraviolet light permeable filter glass.
 2. An ultraviolet flawdetection light according to claim 1, wherein the dielectric multi-filmlayer is composed of alternating low refractivity membrane layers andhigh refractivity membrane layers.
 3. An ultraviolet flaw detectionlight according to claim 1, wherein the dielectric multi-film layer iscomposed of plural layers while each single layer is constituted as ahigh refractivity membrane layer which is sandwiched by two lowrefractivity membrane layers.